Method of producing and regenerating regenerable printing forms



Nov. 25, 1969 G. RITZERFELD 3,479,953

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United States Patent O 3,479,953 METHOD OF PRODUCING AND REGENERATING REGENERABLE PRINTING FORMS Gerhard Ritzerfeld, Franzensbader Str. 21, Berlin-Grunewald, Germany Filed Jan. 16, 1967, Ser. No. 609,648 Claims priority, application Germany, Jan. 27, 1966,

Int. Cl. B41m 5/ 04; B41c 1/06 U.S. Cl. 101-470 2 Claims ABSTRACT OF THE DISCLOSURE A regenerable printing form is prepared by forming on a hacking sheet a mirror image of indicia which are to he printed consisting of a hinder material having incorporated therein a transferahle dye, such as a triphenylmethane dye if printing or duplicating is to he carried out in a spirit duplicator, and having also incorporated therein a material adapted to absorh heat or to he heated when exposed to high frequency radiation to an extent such that contactng portions of a transferahle dye-containing transfer layer will he softened and adhered to the mirror image, therehy replenishing the printing form with transferahle dye.

BACKGROUND OF THE INVENTION The present invention is concerned with a method of regenerating regenerable printing forms and with certain transfer sheets used in producing the regenerable printing form.

More particularly, the present invention is concerned with printing forms of the type which are utilized in spirit duplicators and the like and which hroadly comprise a hacking sheet and a mirror image of printing indiciaforming material including a transferahle dye carried by the hacking sheet.

Conventional methods of regenerating printing forms of this type require penetration of the hacking sheet of the printing form by infra-red rays and, consequently, the hacking sheet of the printing form had to he relatively very thin, generally so that the weight per square meter of the printing form hacking sheet had to he between about 30 and 60 grams. However, duplicating with such very thin masters or printing forms causes great diiculties, primarily because the fastening means of the duplicating devices are generally not capable of holding such very thin printing forms or masters in a satisfactory manner and, furthermore, because such very thin printing forms are too'easily creased SUMMARY OF THE INVENT ION The present invention overcomes the above-discussed and other difficulties by making it possible to regenerate printing forms including a hacking sheet of greater thickness, for instance having a weight of between 80` and 110 gr./m.

This is accomplished according to the present invention hy arranging in superposed relationship a hacking sheet of the desired thickness, such as a hacking sheet having a weight of between about 80 and 110 gr./m. and a transfer sheet which includes a layer of pressure sensitive transferahle material having incorporated therein a transferahle dye and a heat radiation ahsorbing material, with one face of the hacking sheet Contacting the transfer layer. Upon exertion of pressure against the other face of the hacking sheet, corresponding portions of the transfer layer will he adhered to the hacking sheet, forming on the face thereof which is opposite the face against which pressure is directly exerted, a mirror image of the pressure-exposed portions of the other face. Upon separation of the thus formed printing form, it is possible to make copies of the initial imprint hy moistening the mirror image thereof formed a't the opposite side or face of the hacking sheet and Contacting the moistened portions with a copy sheet. In other words, the copies may then 'he produced hy a conventional duplicating method.

After the transferahle dye contained in the mirror image-forming portions is suhstantially exhausted, the hacking sheet may he regenerated by superposing the indicia-carrying face of the printing form onto a transfer sheet carrying, at the face thereof which contacts the indicia forming-portions of the printing form, a transfer layer consisting of a heat-sensitive transferahle material which will he softened upon being heated and which has a transferahle dye incorporated therein. By thereafter exposng the other face of the hacking sheet, while the latter is in contact with the transfer sheet, to heat radiation or high frequency radiation, the heat radiation or high frequency ahsorbing material of the mirror image portions will he heated to a temperature sufliciently high to at least soften juxtaposed portions of the Contacting transfer layer and to adhere the juxtaposed portions to the mirror image-formng portions on the hacking sheet of the printing form, so that the hacking sheet of the printing form, after separation from the transfer sheet, will carry mirror image portions of the indicia which are to he printed, the outer layer of which will consist of transfer material having distributed therethrough the transferahle dye. The thus regenerated printing form is then ready for use in conventional duplicating.

The present invention is also concerned with a transfer sheet which may be used in preparing the regenerable printing form, which transfer sheet comprises a hacking sheet and a layer of pressure-sensitive transferahle mate- `rial located on one face of the hacking sheet, wherehy the layer of pressure sensitive transferahle material comprises a pressure transferahle hinder material having incorporated therein and distributed therethough a heat radiation absorhing material and a transferahle dye.

The term heat radiation ahsorbing material" is broadly used in the context of the present description and claims as denoting material which upon eXposure to heat radiation or to an electric high frequency field will he heated to a higher temperature than the surrounding material such as the hinder material. It will he accomplished thereby that portions of a heat-transferahle transfer layer in contact with the hacking sheet carrying mirror image indicia including the heat radiation ahsorbing material will he heated to their softening point, to the extent to which such portions of the transfer layer are directed juxtaposed to the mirror image indicia. consequently only portions of the heat sensitive transfer layer which are directly juxtaposed and in contact with the mirror image indicia will he softened and adhered to the mirror image indicia and thus form the outer face of the mirror image of the indicia which are to he copied. Since the transfer layer portions which are thus adhered to the printing form contain transferahle dye, this will result in a regeneration of the printing form.

The transferahle dye may he any dye which can he transferred from the mirror image indicia to a Contacting copy sheet, for instance by a conventional duplicating process.

It will he readily understood that the above-described process may he carried out without consideration of the thickness of the hacking sheet of the printing form, since the above-described method does not require penetration of the hacking sheet of the printing form by infra-red rays or the like.

The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The eight figures of the drawing are schematic elevational cross-sectional views of various arrangements of printing form members, transfer sheets and heat sources, wherein FIG. 1 illustrates the imprinting by means of a typewriter of the backing sheet of the printing form in contact with a transfer sheet of a type which may be utilized in accordance with the present invention;

FIG. 2 illustrates the condition of the printing form and the transfer sheet after imprinting and separation;

FIG. 3 illustrates the regeneration of the printing form produced according to FIG. 2;

FIG. 4 illustrates the regenerated printing form and the residual transfer sheet produced according to FIG. 3;

FIG. 5 illustrates the imprinting by means of a typewriter and with interposition of a color ribbon, of the backing sheet of the printing form utilizing a different type of transfer sheet;

FIG. 6 illustrates the printing form produced according to FIG. 5 after separation from the transfer sheet;

FIG. 7 illustrates the regeneration of the printing form produced according to FIG. 6; and

FIG. 8 illustrates the regenerated printing form produced according to FIG. 7 after the same has been separated from the transfer sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a printing form backing sheet of the desired thickness, for instance having a weight of between about 80 and 110 gr./m. and consisting for instance of paper or synthetic material, is imprinted, for instance in a typewriter or in any other suitable manner which may include writing or imprinting in suitable printing machines, while being in contact with a transfer sheet carrying, in contact with the backing sheet of the printing form, a pressure sensitive transfer layer, so that, -upon exertion of pressure by imprinting the 'backing sheet, corresponding portions of the transfer layer will be adhered to the opposite face of the backing sheet, forming thereon a mirror image of the imprint. The pressure sensitive transfer layer has incorporated therein heat radiation absorbing material, for instance graphite or carbon black particles, as well as a transferable dye, for 'instance a triphenylmethane dye such as is conventionally used in spirit duplicating processes. It is also possible to have the backing sheet of the printing form superposed upon a composite transfer layer comprising an outer layer consisting of pressure sensitive transfer material having heat radiation absorbing material such as described above, or possibly other similarly suitable pigments or the like, incorporated therein, and also including a second layer of pressure .sensitive transfer material interposed between the backing sheet of the transfer sheet and the heat radiation absorbing materialcontaining layer, which second layer contains the transferable dye. Upon imprinting of the backing sheet of the printing form and thereby transferring mirror imageforming portions of the composite transfer layer from the transfer sheet to the backing sheet of the printing form, the transferred portions of the transferable dye-containing transfer layer will form the outer portion of the mirror image indicia which will be imprinted onto copy sheets or the like.

It should be noted that the specific composition of pressure sensitive transfer layers, as Well as of heat sensitive transfer layers which will be discussed further below, are well known to those skilled in the art and that any of the conventionally utilizd pressure or heat sensitive transfer layers can be used in accordance with the present invention, provided that there are incorporated in these layers the heat radiation absorbing material and/or the transferable dye as will be more fully described herein.

After the thus produced printing form has been utilized for producing in a suitable duplicating device a number of copies thereof so that the printing form has become more or less exhausted, the printing form may be regenerated in accordance with the present invention by being superposed onto a heat sensitive transfer layer having incorporated therein the desired transferable dye, with the exhausted mirror image portions of the printing form contacting the transfer layer.

The transfer layer containing the transferable dye which will be used for regenerating the printing form is supported by a backing sheet but, in addition, may also be covered with a, per se, conventional protective layer also of heat sensitive transfer material. The thus formed assembly is then subjected to infrared radiation or high frequency electric radiation so that such radiation first impinges onto the backing sheet of the transfer layer and passes through the same and through the transfer layer towards the exhausted printing form and the radiation will contact the mirror image indicia on the printing form which are more or less exhausted, with respect to transferable dye content which, however, still include the heat or high frequency waves or radiation-absorbing material. The mirror image indicia, due to their content of heat waves and the like absorbing material, will be heated to a substantially higher temperature than the remainder of the assembly and, consequently, will cause sensitization or softening of juxtaposed contacting portions of the transferable dye-containing heat sensitive transfer layer of the transfer sheet. These juxtaposed, transferable dye-containing portions of the transfer layer will thus be adhered to the mirror image indicia of higher temperature on the backing sheet of the printing form and will become part of the printing form which thereby is regenerated and again made capable of producing copy.

The transfer sheet which is used for regenerating the printing form will thus contain, in the layer or layers thereof which are to be transferred, a material, for instance pigments or carbon black or graphite particles which have a high capacity for being heated by being exposed to infra-red waves or electric high frequency waves, and will also include the transferable dyestulf, preferable triphenylmethane dyes which are well known to those skilled in the art. These active agents of the transfer layer, i.e. the pigments or the like and the dyestuffs are worked into a heat sensitive and binder material which may consist of waXes, oils, fats and/ or synthetic materials.

According to a preferred embodinent of the present invention, the melting points of the heat sensitive transfer materials of the pigments or the like containing layer and of the transferable dye-containing layer are substantially identical, however, the compositions of these layers are so chosen that in solidified condition the graphite, carbon black or the like-containing layer is harder than the layer containing the transferable dye.

According to another and frequently preferred embodiment of the present invention, the triphenyhnethane dyestufs are incorporated in a heat sensitive binder material consisting of wax and fat, and the superposed carbon black or graphite-containing heat sensitive layer consists of 'synthetic materials, the latter having a higher melting point than the wax and fat material of the dyestuffcontaining layer. Preferably, the melting point of the carbon black or graphite-containing layer will be between about and C., and the melting point of the dyestulf-containing layer will be correspondingly lower, preferably below 120 C. or even below 100 C.

It is possible by proceeding in accordance With the present invention to obtain a printing form of the desired high strength, i,e. desired thickness and relatively high weight per square meter of the backing sheet of the print-.-

ing form, and nevertheless to obtain the desired transfer of heat sensitive transfer material by irradiation of the mirror image on the printing form, not through the backing sheet of the printing form but in the direction from the backing sheet of the transfer sheet toward the printing form. Thus, an exhausted printing form which includes a relatively thick backing sheet can be easily and effectively regenerated.

Referring now to the drawing, and particularly to FIG. l, it will be seen that the printing form carrying a mirror image of the original imprint is produced by superposing backing sheet 3 of the printing form upon a transfer sheet which comprises backing sheet 6, carbon black-containing pressure sensitive transfer layer 4 and, interposed therebetween transferable dye-containing pressure sensitive transfer layer 5. Backng sheet 3 is imprinted at' its free face, for instance by means of typewriter key 1, so as to form indicia 2 thereon and simultaneously to exert pressure onto portions of transfer layers 4 and 5 which are juxtaposed to indicia 2. Thereby, the pressure sensitive juxtaposed portions of transfer layers 4 and 5 will be adhered to backing sheet 3 and the thus formed printing form may then be separated from the residual portion of the transfer sheet.

It will be seen that the printing form shown in FIG. 2 consists of backing sheet 3 having on one face thereof indicia 2 and having on the other face thereof mirror images of indicia 2 formed of portions 8 of the transferable dye-containing transfer layer and, interposed between portions 8 and the backing sheet, portions 7 of carbon black, graphite or the like-containing transfer layer. Residual portions of transfer layers 4 and 5 which remain adhered to the backing sheet 6 of the transfer sheet are indicated in FIG. 2 by reference numerals 9 and 10 respectively.

After forming, for instance by a conventional spirit duplicating method, a number of copies of the printing form or master shown in FIG. 2 and thereby exhausting a substantial part of the transferable dye-containing portion 8 of the mirror image indicia, the thus at least partly exhausted printing form may be regenerated, as illustrated in FIG. 3, by being superposed upon a color transfer sheet comprsing a backing sheet 12 and a heat sensitive transfer layer 11 having the transferable dye incorporated therein. The thus formed assembly is exposed to infra-red radiation emanating for instance from a source 13 of infra-red radiation, which first impinges the free face of backing sheet 12 of the dye transfer sheet and passes through backing sheet 12 and the dye transfer layer into the mirror image indicia on the backing sheet 3 of the printing form. Portions 7 of the mirror image indicia which include the carbon black or the like will be heated to a relatively high temperature by the infra-red radiation and will cause heating of the portions of heat sensitive, transferable dye-containing transfer layer 11 which contact the mirror image portions of the printing form to a temperature sufficiently high to cause adherirg of these juxtaposed portions of transfer layer 11 to the mirror image-forming portion of the printing form.

The heating of the mirror image portions of the printing form may also be carried out by exposure to electric high frequency waves rather than infra-red waves.

As shown in FIG. 4, after separating the thus regenerated printing form from the dye transfer sheet, portions 14 of the dye transfer layer 11 now adhere to and form part of the mirror image-forming portions of the printing form, whereas portions 15 of dye transfer sheet 11 which were not juxtaposed to the mirror image-forming portions of the printing form remain adhered to backing sheet 12 of the transfer sheet.

This is accomplished, as illustrated, by the radiation of the assembly by means of nfra-red radiator 13. The infrared rays pass through the transfer sheet and the transfer dye-containing outer layer of the mirror image portion of the printing form and contact the mirror image portions 7 of the printing form which include particles of carbon black or the like. These particles absorb the infra-red radiation and are heated thereby, so that the corresponding portions of layer 11 will be transferred at mirror image portions 14 from the transfer sheet to the printing form while the residual portions of the transfer layer which were not thus exposed to heat will remain fixed to the backing sheet 12 of the transfer sheet.

This regenerating of the more or less exhausted printing form can be repeated as often as desired.

The initial imprinting of backing sheet 3 may be carried out with or without interposition of a color ribbon or the like. Since the new transfer dye-containing material will be adhered only to the carbon black of the like-containing mirror image portions 7, the new mirror image portions 14 which are adhered to the printing form upon regeneration of the same -will represent a sharply defined mirror image of the original imprint 2 and thus will be capable of producing a sharply defined copy.

FIG. 5 illustrates a process somewhat similar to that illustrated in FIG. l with the exception that transfer layer 16 is a single transfer layer having incorporated therein the transferable dye as well as carbon black or other heat radiation absorbng pigment or the like.

Upon imprinting of backing sheet 3 -by means of type- -writer key 1 and an interposed color ribbon, legible indicia 2 will be formed and simultaneously, the pressure exerted by imprinting (which may be replaced by writing with pencil, stylus, or other printing methods) will cause transfer of portions of pressure sensitive transfer layer 16 from backing sheet 6 of the transfer layer to backing sheet 3 of the printing form. The transferred portion 17 will represent an exact mirror image of indicia 2.

After separating the assembly which has been subjected to imprinting, the printing form as illustrated in FIG. 6 will be available for producing copies thereof. Upon producing copies, for instance in a spirit duplicator, the transferable dye of mirror image portion 17 will -be eventually exhausted, whereas the carbon black portion thereof will remain unalfected. After the printing form has been substantially exhausted, the same may be regenerated, for instance as illustrated in FIG. 7, by being superposed upon another transfer sheet, compr-ising a backing sheet 12 and a heat transferable transfer layer 11 containing transferable dye.

By applying infra-red radiation emanating from the device indicated by reference numeral 13, portions of transfer layer 11, which exactly correspond to the Outline' of the carbon black or the like-containing mirror image portions 17, will be molten and adhered to mirror image portions 17 so that upon separation the regenerated printing form illustrated in FIG. 8 will become available. Since the `'o'riginally applied carbon black is not soluble in alcohol or water and alcohol, the portions 17 will remain permanently in contact with backing sheet 3 and upon exhaustion of the regenerated transferable water or alcohol soluble dye-containing portions 14, regeneration as illustrated in FIGS. 7 and 8 may be repeated.

As has been pointed out further above, conventional and well known transfer compositions which may be pressure and/or heat sensitive may be used for forming the transfer layers which are utilized in accordance with the present invention, by incorporating into these transfer compositions carbon black or the like and/or transferable dyes'such as for instance triphenylmethane dyes.

The following examples giving specific compositions of transfer layers which may be advantageously used in *accordance with the present invention are therefore given as illustrative only without, however, limiting the invention to the specific details of the examples.

The thickness of the individual transfer layers which are utilized according to the present invention is also conventional, however, as pointed out above, it is possible according to the present invention to produce and regenerate printing forms including a relatively heavy backing sheet and to utilize in the production of these printing forms and in the regeneration of the same transfer sheets which include a relatvely thin or light weight backing sheet.

EXAMPLE 1 A transfer sheet for transferring mirror image portions of a transfer layer including a transferable dye and a heat or high frequency radiation sensitive material may be composed as follows:

Grams Carnauba wax 1,200 Bees wax 500 Petroleum jelly 1,200 Wool fat 500 Mneral oil 1,500 Crystal violet 5,000 Carbon black 500 EXAMPLE 2 A transfer layer containing transferable dye may be composed as follows:

Grams Carnauba wax 1,200 Bees wax 500 Petroleum jelly 1,200 Wool fat 500 Mineral oil 1,500 Crystal violet 6,000

The above-described transferable dye-containing transfer layer may -be protected by a protective coatng consisting of:

Grams Parafiin 75 Ozocerite 10 Carbon black 15 EXAMPLE 3 A composite transfer layer may consist of the transferable dye-containing transfer layer of Example 2 interposed between a backing sheet and an outer transfer layer consisting of Grams Candelilla wax 75 Paraffin 10 Carbon black 15 EXAMPLE 4 A preferred embodiment of a transfer sheet may comprise a conventional backing sheet carrying a transferable dye-containing transfer layer composed as described in Example 2 and superposed thereon a layer formed of 5 parts of a dispersion consisting of:

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended clams.

I claim:

1. A method of preparing a regenerable printing form for use in spirit duplicators and the like, comprising the steps of arranging in superimposed relationship a backing sheet and a transfer sheet including a composite layer of transfer material and comprising in superimposed relationship a first layer of transfer material having a transferable dye incorporated therein and a second layer of transfer material in contact with one face of said backing sheet, said second layer having a heat radiation absorbing material incorporated therein; exerting pressure against the other face of said backing sheet so as to adhere corresponding portions of said transfer layer to said one face of said backing sheet forming thereon a mirror image of the pressure-exposed portions of said other face; and separating the thus-formed printing form from the residual portion of said transfer sheet.

2. A method of preparing and regenerating a regenera- 'ble printing form adapted for use in spirit duplicators and the like comprising the steps of arranging in superimposed relationship a backing sheet, and a transfer sheet including a layer of transfer material having incorporated therein a transferrable dye and a heat radiaton absorbing material, 'with one face of said backing sheet Contacting said transfer layer; exerting pressure against the other face of said backing sheet so as to adhere corresponding portions of the transfer layer to said one face of said backing sheet forming thereon a mirror image of the pressure-exposed portions of said other face; and separating the thus-formed printing form from the resdual portion of said transfer sheet; and regenerating said printing form after at least partial exhaustion of the transferrable dye thereof, said regenerating comprising the steps of arranging said printing form, carrying on one face of the backing sheet thereof partially exhausted mirror image portions formed of transfer material having heat radiation absorbing material still incorporated therein, in superimposed relationship with a transfer sheet including a second backing sheet and a transfer layer having a transferrable dye incorporated therein, with said transfer layer Contacting said mirror image portions-carrying one face of said second backing sheet; exposing the free face of said second backing sheet while said transfer layer is in contact with said partially exhausted printing form to heat radiation so as to heat the heat radiation absorbing material of said mirror image to a temperature sufiiciently high to at least soften juxtaposed portions of said contacting transfer layer and to adhere said juxtaposed portions to said mirror imageforming portions and thereby to said backing sheet of said printing form, thereby regenerating the latter; and separating the thus-regenerated printing form from the residual portion of said transfer layer.

References Cited UNITED STATES PATENTS 3,054,692 9/1962 Newman et al. 250-65.1XR

3,177,086 4/1965 Newman et al. 250-65.1XR

3,246,148 4/ 1966 T roeyer et al.

3,359,900 12/1967 Newman 101-468 i FOREIGN PATENTS 1,012,302 12/ 1965 Great Britain.

ROBERT E. PULFREY, Primary Examner F. FREI, Assistant Examiner U.S. Cl. X.R. 

